1. Field of the Invention
The present invention relates to image data processing in which an image frame store has many storage devices, such as disk drives, configured to store image frames of a predetermined definition.
2. Description of the Related Art
It is known to store image frames, such as frames forming part of a video or cinematographic film, on arrays of disk drives, as disclosed in U.S. Pat. Nos. 6,055,354 and 6,118,931. Each image frame is divided into a plurality of stripes and data from said stripes is written to or read from an array of disks in parallel. Preferably, the array includes redundancy such that, should a disk crash occur, it is possible for lost data to be reconstituted. Furthermore, such an approach allows relatively inexpensive disks to be used therefore it is known for configurations of this type to be referred to as a redundant array of inexpensive disks, usually abbreviated to the acronym RAID.
When image frames are written to a disk array, each image frame is divided into a plurality of stripes with one disk receiving the data derived from one stripe. In this way, the number of stripes present within the image equates to the number of disks being used in the array. The actual number of stripes required for a particular image, for a given disk transfer speed and storage capacity, will depend upon the size of the image frames themselves. Thus, in many systems, it is possible to process standard NTSC/PAL video signals in combination with much larger image frames possibly generated under the high definition video protocol or derived form scanning cinematographic film.
It is known to partition an array of disks such that each partition is configured to provide optimal transfer of image frames at a particular definition. Once partitioned in this way, each partition only receives or supplies frames of the definition under consideration therefore its file structure may be optimised by taking account of this constraint. Thus, such an approach differs significantly from general purpose operating systems in which frames may be stored as files within a directory structure.
A computer program that processes image frames stored in the aforementioned format is licensed by the present Assignee under the trademark “FLAME”. Flame and its related products has a native file system which optimises the transfer of image frame data to and from disk storage devices. Such an approach optimises operational characteristics where great emphasis is placed on being able to transfer large quantities of image data for real-time viewing or multiple real-time processing.
In addition to operating with a storage system that is optimised for transferring frames of constant definition, the user interface of the Flame system is constrained so as to be more sympathetic to existing video/film editing/effects processing. Thus, within the native Flame environment, data is not divided up into levels of directories and sub-directories, as is often the case with general purpose processing environments. Thus, within the native frame store system, there is a notion of a clip library for a particular project that may contain desktops, reels and clips. A reel may be contained within a desk top and a clip may be contained within a reel. A clip consists of a plurality of contiguous frames and thereby maintains the analogy with the physical editing of cinematographic film.
Flame is one of many programs that is capable of directly processing image frames stored in the native format. However, an increasing number of useful image processing applications are available that have been developed for execution within a general purpose processing environment. In order to achieve this, it is known to export frames from the native system such that the frame data is stored again in a file-based configuration. However, a problem with this known approach is that it is necessary to make multiple copies of the data thereby significantly increasing storage requirements. In addition, procedures of this type result in several versions of the data being generated such that problems may occur in terms of identifying the most recent. Furthermore, when storing data in conventional file-based systems, reductions will occur in terms of the rate of data transfer thereby limiting the system's ability to transfer and display image frames in real-time.